Proteins antigenically similar to the p30 protein of the murine and feline leukemia viruses have been identified in benign and malignant prostatic tissue. Malignant prostatic tissue will be examined by electron microscopy in a longitudinal study employing serial biopsies in patients undergoing either endocrine therapy, radiation therapy or chemotherapy to determine (a) the response or appearance of virus-like particles, (b) the persistence or appearance of treatment-resistant cells and their ultrastructural characteristic, (c) the alterations in cell surface charge in these prostatic cancer cells before and after treatment application, and (d) the relationship of these observations to the response of the patient and his malignancy to the treatment modality selected in order to establish potential predictors as to treatment selection and response.